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General Mechanical

General Mechanical

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Modelling stress relaxation for viscoelastic material with many time steps

    • Thies Blaakman
      Subscriber

      Dear all,

      I'm trying to model the stress relaxation behaviour of a material after deforming it. I have curve fitted the Prony series for this model to make my material behave viscoelastically and I have some generic linear elastic properties. In order to deform the model, I need many time steps in order to have a converging solution, but these timesteps already include some stress relaxation behaviour due to the viscoelastic material model. I would like to create a seemingly instantaneous linear elastic deformation, then activate the viscoelastic properties and see what happens. I have tried using the MPCHG command, but this of course does not work for nonlinear material models. Is there anyone who can give me a lead on this?

      With kind regards,

      Thies

    • Giorgos Papa
      Ansys Employee

      Hello Thies,

       

      Unfortunately it is not possible to turn off/on the viscoelasticity like we allow for creep.

      One thing you can do is run the first load step with a very small time to make the rate dependency negligible.

       

      Kind Regards,

      Giorgos

      • Thies Blaakman
        Subscriber

        Dear Giorgos,

        That's kind of the problem. If I don't use many time steps to subdivide my deflection, I won't have convergence. Is there maybe a way to solve my model elastically, and then load it in a different file with a different material model in which I add the viscoelasticity? 

        With kind regards,

        Thies

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